16531 has 4 divisors (see below), whose sum is σ = 16864. Its totient is φ = 16200.

The previous prime is 16529. The next prime is 16547. The reversal of 16531 is 13561.

16531 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13561 = 71 ⋅191.

It is a 4-Lehmer number, since φ(16531) divides (16531-1)⁴.

It is a cyclic number.

It is not a de Polignac number, because 16531 - 2¹ = 16529 is a prime.

It is a super-2 number, since 2×16531² = 546547922, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75 + ... + 196.

It is an arithmetic number, because the mean of its divisors is an integer number (4216).

2¹⁶⁵³¹ is an apocalyptic number.

16531 is the 58-th centered decagonal number.

16531 is a deficient number, since it is larger than the sum of its proper divisors (333).

16531 is an equidigital number, since it uses as much as digits as its factorization.

16531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332.

The product of its digits is 90, while the sum is 16.

The square root of 16531 is about 128.5729364991. The cubic root of 16531 is about 25.4741504036.

It can be divided in two parts, 165 and 31, that multiplied together give a palindrome (5115).

The spelling of 16531 in words is "sixteen thousand, five hundred thirty-one".